The present invention relates to controlled release compositions comprised of porous polymeric microbead carriers retaining vitamins within their pores. The invention further relates to methods of preparing such compositions and their methods of use.
Vitamins are chemically unrelated, fairly complex organic substances that are essential in small amounts for the maintenance of normal metabolic functions. Vitamins are not synthesized within the human body and must therefore be furnished from exogenous sources. Natural sources of vitamins include plant and animal tissue.
Vitamins can be broadly categorized as either fat-soluble or water-soluble. Vitamins A, D, E and K are fat soluble and are absorbed in association with lipids. Vitamins B.sub.1, B.sub.2, B.sub.5, B.sub.12, B.sub.15, B.sub.17, C, niacin, folic acid, pantothenic acid, biotin, bioflavonoids, choline, inositol and F are examples of water-soluble vitamins.
Vitamins A, D and E, and derivatives thereof, including esters such as vitamin A palmitate, vitamin E acetate and vitamin E palmitate and substances which contain such vitamins and vitamin derivatives, such as fish oils, have long been known to be useful for various topical therapeutic and cosmetic purposes. Creams, ointments and powders containing vitamins A and D as such or in cod liver oil have been used for the prevention and treatment of prickly heat and diaper rash in infants. Vitamin E and vitamin E esters, such as the acetate and palmitate, have been used, typically in creams, ointments, lotions, oils and other cosmetic formulations, as skin moisturizers and smoothers, to treat chronic skin diseases, to aid in healing burns and wounds, to reduce scarring from wounds, as topical anti-inflammatory agents, and to protect the skin from damage from ultraviolet rays.
Vitamin-containing therapeutic and cosmetic creams, ointments, lotions, oils and like formulations feel greasy or oily when applied, and often leave residues which are difficult to remove from the skin. Vitamin-containing powder preparations enable only limited amounts of vitamin to penetrate the skin.
Vitamins are also used as additives in preparations primarily intended for purely cosmetic use, such as lip balms, lipsticks, blushers, eyeshadows and foundations.
Retinoids are a group of compounds consisting of vitamin A and its analogs. In addition to their effectiveness in enhancing vision and fertility, the compounds in this group are effective as keratolytic agents, and as such are used topically to retard and ameliorate photoaging of facial skin and senile keratosis, to treat acne vulgaris, and to treat warts.
Vitamin A itself is a term used to designate several biologically active compounds, principally the alcohols retinol, whose chemical name is 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetrae-nol, and 3-dehydroretinol. Other retinoids include the corresponding acids, aldehydes, esters and aromatic derivatives of these. The most common of the acids is retinoic acid, or 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraenoic acid. The all-trans-form, of retinoic acid is also known by the common name tretinoin. Other acids within the class include the 9,10-cis-form and the 13-cis-form. Examples of esters are the methyl ester and the ethyl ester. The acids are crystalline under ambient conditions, soluble in fats and alcohols. The esters are liquids under ambient conditions. The acids and their derivatives are of particular interest for their high therapeutic value.
For topical application, retinoids are typically formulated as creams, ointments, oils and the like. In such formulations, however, retinoids rapidly degrade and lose activity. In addition, moderate to severe skin irritation frequently results from the use of these formulations. Still further, these formulations usually feel oily or greasy when applied, and tend to leave residues on the skin which are difficult to remove.